In the field of automotive electronics, it is known to provide automotive networks in a vehicle in order to interconnect a number of functional units distributed about the vehicle, for example remote sensor devices and actuators and control units. In order to achieve this aim, the automotive network has to provide a robust moderate speed interconnection between a primary node and satellite nodes. One known topology of a typical automotive network is a master-slave network topology, where a master module sends data to one or more slave modules over a bus and the one or more slave modules respond to the master module using the bus. The automotive network is therefore specified or standardised at a data level in relation to message protocols and classes, formats, bit transmission orders and a method of programming devices having programmable addresses. For example, known protocols that can be used for the automotive network include the Local Interconnect Network (LIN) or Controller Area Network (CAN) protocols.
One example application of the automotive network is communication between ultrasonic parking sensor modules and a central master module. For this application, the sensor modules constitute slave modules and can comprise a microprocessor, a power supply and a transducer. In this example, the master module initiates emission of ultrasonic waves by the slave modules and then receives and interprets data transmitted back by the slave modules. Of course, other applications exist, for example heating and climate control applications, keypad control and/or control of any other de-centralised human interface.
However, with the advance and increase of technology incorporated into vehicles, both hardware and software, Electronic Control Units (ECUs) constituting the master and slave modules in the automotive network are being required to perform increasingly complex tasks and hence require increased computing power. The increased computing power demanded requires a corresponding increase in supply current in order to power the ECUs adequately. Additionally, the increased complexity of some of the tasks that need to be performed have associated higher information exchanges between the master module and the slave modules requiring increased data communication rates. However, in order to reduce Radio Frequency (RF) emissions in order to provide Electromagnetic Compatibility (EMC) compliance and to withstand Electrostatic Discharge (ESD) events, capacitors are provided on the bus mentioned above. Whilst provision of the capacitors has the positive benefits mentioned above, the capacitors limit the data rates achievable using the automotive network. Examples of buses that suffer from this drawback are the bus used for Peripheral Sensor Interface (PSI5) specification and the bus used in the Distributed System Interface (DSI) specification. Additionally, these buses are unable to support the additional electrical power requirements mentioned above.
Whilst the physical “lines” that support the LIN protocol mentioned above are able to support the above speed and power requirements, the so-called “LIN bus” is a three-line/wire bus and, due to environmental considerations as well as cost implications, it is desirable to reduce the number of lines forming the communications bus of the automotive network. The bus also needs to support full duplex communications.